The present invention relates to a stackable networking device, especially to a dual-speed stackable hub having a switch control circuit for preventing a traffic loop occurred in a stack of the dual-speed stackable hubs.
The use of computer networks has gradually increased in industry, commerce, and even in personal applications. The local area network (LAN) connects computers, peripherals, and communication devices, through appropriate links, sharing the resources, sharing information, and exchanging data. Local area networks are commonly used in small and middle-size companies.
FIG. 1 shows the commonly used N number double speed switch hub formed network stacks. Every unit of the stacks has repeaters of different transfer speeds (10 Mbps and 100 Mbps). To transfer data between the ports of the repeaters, two stacks each connect the repeaters of the same speed. Each exchange switch of a unit connects with one 10 Mbps repeater and the 100 Mbps repeater. The ports of the repeaters connect to the ports of other exchange switches of different transfer speeds (such as port I and port J in FIG. 1).
FIG. 1 shows multiple stackable networking devices 13 arranged in a stack. These stackable networking devices 13 are usually referred to as dual-speed Ethernet Hubs. Each of these stackable networking devices 13 has an exchanging unit 14 for automatically exchanging packets between two internal repeaters 11, 12 of 10 and 100 Mbps data transfer rates when a cable is connected to port I or port J. Since there is no communication among these exchanging units 14, so if one of these exchanging units is down, the remaining exchanging units 14 will still keep transmitting packets. It will cause more traffic in the stack buses and waste the bandwidth of the networking device 13. Moreover, when broadcast packets are sent to the stack of the stackable networking devices 13, a traffic loop is likely to be formed in the stack. The traffic loop causes more traffic in the bandwidth of the dual-speed Ethernet hubs and thus congests the networks.
A conventional method for solving the traffic loop problem is to perform a Spanning Tree Protocol by implementing a Central Process Unit (CPU) in each exchanging unit 14. However, the implementation of a CPU will inevitably increase the cost of the dual-speed Ethernet Hub.
It is an object of the present invention to provide a dual-speed stackable networking device capable of preventing a traffic loop by implementing a switch control circuit in the stackable networking device.
It is another object of the invention to provide a cost-effective dual-speed stackable networking device which can save the cost of CPU by implementing a simple switch control circuit for controlling the operations of the exchanging unit.
A first stack bus connects with all the first signal repeaters of every dual-speed stackable networking device, to exchange data between the first repeater of every dual-speed stackable working device. A second stack bus connects with all of the second repeaters of every dual-speed stackable net working device, to exchange data among the second repeaters of each dual-speed stackable networking device. One switch control circuit is added to each dual-speed stackable networking device, which includes some switch control circuits connected to the same switch control circuit of the other dual-speed stackable networking device. These circuit units switch control circuit have an output end for sending a high or low voltage signal to the next circuit unit of the other switch control circuit. It has an input end for receiving a high or low voltage signal from the other switch control circuit and a detector connected with the exchanging unit. The switch control circuit generates a high voltage signal when the exchange switch is on. A logic unit is connected with the input end, and the detector and exchanging unit. When the signal from the input end is low and the signal from the exchanging unit is high, the logic unit generates a high volume signal to the output end and makes the next exchanging unit on. It generates a low voltage signal to the next exchanging unit and turns the next exchanging unit off, when the signal from the input end is high.
The repeaters of the above-mentioned design are typically either of transfer speed of 10 Mbps or 100 Mbps. The stack buses of the switch control circuit typically have transfer data rates of 10 Mbps or 100 Mbps.
The logic unit, as described above, has the following components: an and/or gate connects the input end of the switch control circuit and the output of the detector. When it receives a high voltage signal from the input end or from the detector, it sends out a high voltage signal. One Normally Open Mechanical Relay connects with the input end and output end of the switch control circuit. The Relay is open when the exchanging unit is on, and it is closed when the exchanging unit is off. The Relay transfers the signal from the input end to the output end when the exchanging unit is off.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.